Analytic solutions to the accretion of a rotating finite cloud towards a central object - II. Schwarzschild spacetime

We construct a general relativistic model for the accretion flow of a rotating finite cloud of non-interacting particles infalling onto a Schwarzschild black hole. The streamlines start at a spherical shell, where boundary conditions are fixed, and are followed down to the point at which they either cross the black hole horizon or become incorporated into an equatorial thin disc. Analytic expressions for the streamlines and the velocity field are given, in terms of Jacobi elliptic functions, under the assumptions of stationarity and ballistic motion. A novel approach allows us to describe all of the possible types of orbit with a single formula. A simple numerical scheme is presented for calculating the density field. This model is the relativistic generalisation of the Newtonian one developed by Mendoza, Tejeda, Nagel, 2009 and, due to its analytic nature, it can be useful in providing a benchmark for general relativistic hydrodynamical codes and for exploring the parameter space in applications involving accretion onto black holes when the approximations of steady state and ballistic motion are reasonable ones.Comment: 12 pages, 6 figures, references and minor changes added to match version accepted for publication in MNRA

An analytic toy model for relativistic accretion in Kerr spacetime

We present a relativistic model for the stationary axisymmetric accretion flow of a rotating cloud of non-interacting particles falling onto a Kerr black hole. Based on a ballistic approximation, streamlines are described analytically in terms of timelike geodesics, while a simple numerical scheme is introduced for calculating the density field. A novel approach is presented for describing all of the possible types of orbit by means of a single analytic expression. This model is a useful tool for highlighting purely relativistic signatures in the accretion flow dynamics coming from a strong gravitational field with frame-dragging. In particular, we explore the coupling due to this between the spin of the black hole and the angular momentum of the infalling matter. Moreover, we demonstrate how this analytic solution may be used for benchmarking general relativistic numerical hydrodynamics codes by comparing it against results of smoothed particle hydrodynamics simulations for a collapsar-like setup. These simulations are performed first for a ballistic flow (with zero pressure) and then for a hydrodynamical one where we measure the effects of pressure gradients on the infall, thus exploring the extent of applicability of the ballistic approximation.Comment: 15 pages, 8 figures, references and minor changes added to match version accepted for publication in MNRA

Evaluación de sustentabilidad de agroecosistemas cafetaleros en Vitoc, Junín, Perú

El objetivo de la investigación fue evaluar la sustentabilidad de los agroecosistemas cafetaleros conducidos por los agricultores familiares del distrito de Vitoc, Región Junín. Se eligieron seis localidades del distrito y dentro de cada localidad, en forma proporcional, las propiedades de los agricultores familiares. Se evaluaron las dimensiones económicas (rentabilidad, ingreso neto mensual y riesgo económico), ambiental (conservación de la vida del suelo, riego de erosión y manejo de biodiversidad) y social (satisfacción de las necesidades básicas, integración social y conciencia ecológica) y el Índice de Sustentabilidad General. Asimismo, para considerar que el agroecosistema es sustentable, se consideró que el indicador debe ser mayor a 2 en todas las dimensiones y en el índice general. Los resultados muestran que los indicadores obtenidos para las dimensiones económica, ambiental, social y el índice general son favorables y orientan hacia una agricultura sustentable. Sin embargo, presenta problemas con la diversificación de los cultivos para la venta, protección del suelo y la cobertura sanitaria, las que pueden ser considerados como una debilidad del agroecosistema. Se concluye que, para las condiciones del estudio, los agroecosistemas cafetaleros conducidos por los agricultores familiares son sustentables

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

Background Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide.Methods A multimethods analysis was performed as part of the GlobalSurg 3 study-a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital.Findings Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3.85 [95% CI 2.58-5.75]; p<0.0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63.0% vs 82.7%; OR 0.35 [0.23-0.53]; p<0.0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer.Interpretation Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised

A validation model to reduce non-contributory time based on Lean tools: Case of a construction company in Perú

AbstractThe construction industry has long been suffering from high rates of non-contributory time. Construction processes are likely to include time, which is sometimes lost for non-value-adding operations resulting in time waste. Considering the large percentage of lost time in all operations, this study aims to reduce the high rate of non-contributory time (NCT) in construction services. To test the management model, a Peruvian company was selected as a study case. In this respect, a management model based on mostly implemented Lean tools such as Kanban, 5S, and TPM was utilized. It is of utmost importance to emphasize that this proposal aims to reduce the NCT by up to 25%, as well as reduce the number of orders generated with delay, and eventually reduce the loss or damage of materials and equipment stoppages

Long-lasting insecticide-treated house screens and targeted treatment of productive breeding-sites for dengue vector control in Acapulco, Mexico

Background Long-lasting insecticidal net screens (LLIS) fitted to domestic windows and doors in combination with targeted treatment (TT) of the most productive Aedes aegypti breeding sites were evaluated for their impact on dengue vector indices in a cluster-randomised trial in Mexico between 2011 and 2013. Methods Sequentially over 2 years, LLIS and TT were deployed in 10 treatment clusters (100 houses/cluster) and followed up over 24 months. Cross-sectional surveys quantified infestations of adult mosquitoes, immature stages at baseline (pre-intervention) and in four post-intervention samples at 6-monthly intervals. Identical surveys were carried out in 10 control clusters that received no treatment. Results LLIS clusters had significantly lower infestations compared to control clusters at 5 and 12 months after installation, as measured by adult (male and female) and pupal-based vector indices. After addition of TT to the intervention houses in intervention clusters, indices remained significantly lower in the treated clusters until 18 (immature and adult stage indices) and 24 months (adult indices only) post-intervention. Conclusions These safe, simple affordable vector control tools were well-accepted by study participants and are potentially suitable in many regions at risk from dengue worldwide

Evaluación de sustentabilidad de agroecosistemas cafetaleros en Vitoc, Junín, Perú

The objective of the research was to evaluate the sustainability of coffee agroecosystems managed by family farmers in the Vitoc district, Junín Region. Six localities of the district were chosen and within each locality, proportionally, the properties of family farmers. The economic (profitability, monthly net income and economic risk), environmental (conservation of soil life, erosion risk and biodiversity management) and social dimensions (satisfaction of basic needs, social integration andecological awareness) and the General Sustainability Index were evaluated.Likewise, to consider that the agroecosystem is sustainable, it is considered that the indicator must be greater than 2 in all dimensions and in the general index. The results showthat the indicators obtained for the economic, environmental and social dimensions and the general index are favorable and oriented towards sustainable agriculture.However, it presents problems with the diversification of crops for sale, soil protection and sanitary coverage, which can be considered as a weakness of the agroecosystem. It is concluded that, for the conditionsof the study,coffee agroecosystems managed by family farmers are sustainable.El objetivo de la investigación fue evaluar la sustentabilidad de los agroecosistemas cafetaleros conducidos por los agricultores familiares del distrito de Vitoc, Región Junín. Se eligieron seis localidades del distrito y dentro de cada localidad, en forma proporcional, las propiedades de los agricultores familiares. Se evaluaron las dimensiones económicas (rentabilidad, ingreso neto mensual y riesgo económico), ambiental (conservación de la vida del suelo, riego de erosión y manejo de biodiversidad) y social (satisfacción de las necesidades básicas, integración social y conciencia ecológica) y el Índice de Sustentabilidad General. Asimismo, para considerar que el agroecosistema es sustentable, se consideró que el indicador debe ser mayor a 2 en todas las dimensiones y en el índice general. Los resultados muestran que los indicadores obtenidos para las dimensiones económica, ambiental, social y el índice general son favorables y orientan hacia una agricultura sustentable. Sin embargo, presenta problemas con la diversificación de los cultivos para la venta, protección del suelo y la cobertura sanitaria, las que pueden ser considerados como una debilidad del agroecosistema. Se concluye que, para las condiciones del estudio, los agroecosistemas cafetaleros conducidos por los agricultores familiares son sustentables

Improved tools and strategies for the prevention and control of arboviral diseases: A research-to-policy forum

Background Research has been conducted on interventions to control dengue transmission and respond to outbreaks. A summary of the available evidence will help inform disease control policy decisions and research directions, both for dengue and, more broadly, for all Aedes-borne arboviral diseases. Method A research-to-policy forum was convened by TDR, the Special Programme for Research and Training in Tropical Diseases, with researchers and representatives from ministries of health, in order to review research findings and discuss their implications for policy and research. Results The participants reviewed findings of research supported by TDR and others. Surveillance and early outbreak warning. Systematic reviews and country studies identify the critical characteristics that an alert system should have to document trends reliably and trigger timely responses (i.e., early enough to prevent the epidemic spread of the virus) to dengue outbreaks. A range of variables that, according to the literature, either indicate risk of forthcoming dengue transmission or predict dengue outbreaks were tested and some of them could be successfully applied in an Early Warning and Response System (EWARS). Entomological surveillance and vector management. A summary of the published literature shows that controlling Aedes vectors requires complex interventions and points to the need for more rigorous, standardised study designs, with disease reduction as the primary outcome to be measured. House screening and targeted vector interventions are promising vector management approaches. Sampling vector populations, both for surveillance purposes and evaluation of control activities, is usually conducted in an unsystematic way, limiting the potentials of entomological surveillance for outbreak prediction. Combining outbreak alert and improved approaches of vector management will help to overcome the present uncertainties about major risk groups or areas where outbreak response should be initiated and where resources for vector management should be allocated during the interepidemic period. Conclusions The Forum concluded that the evidence collected can inform policy decisions, but also that important research gaps have yet to be filled